1. Field of the Invention
This invention relates to an imaging apparatus and an imaging method for imaging a specimen obtained by injecting fluid into a well and particularly to a technology for adjusting illumination light for illuminating the specimen in imaging.
2. Description of the Related Art
In medical or biological science experiments, cells or the like cultured in liquid or gel-like fluid injected into each well of a plate-like device in which a multitude of recesses called wells are arranged are, for example, observed and measured as a specimen. Such a device is, for example, called a microplate or a microtiter plate. In recent years, specimens are imaged by a CCD camera or the like and made into digital image data, and various image processings are applied to the image data for observation and analysis.
In this case, even if a light quantity distribution of illumination light irradiated to the specimen is made uniform, the quantity of light incident on the content (cells or the like) of the specimen may become nonuniform depending on the position due to light refraction caused by the meniscus of the surface (liquid surface) of the specimen and brightness nonuniformity resulting from this may be reflected on an image. As a conventional technology focusing on such a problem, in a technology disclosed in the specification of U.S. Pat. No. 7,718,131 for example, the density nonuniformity of an image resulting from the nonuniformity of illumination light is solved by reassembling an image of one well from partial images obtained by imaging in different incident directions of light a plurality of times.
In the conventional technology above, the incident direction of light is merely switched and light quantity shortage at a part where incident light is originally unlikely to reach, e.g. at a peripheral edge part of the recess is not solved. Thus, this has not gone far enough to make the quantity of light incident on the content of the specimen uniform. Such nonuniformity in the quantity of incident light causes luminance nonuniformity in an image of the content (cells or the like) of the specimen. For example, the luminance of an analysis object such as cells included in an image is used as important information at the time of automatic analysis such as the detection of cells and the discrimination of the type of the cells by image analysis. Nonuniformity in the incident light quantity reduces the accuracy of such an analysis and this problem cannot be dealt with in the above conventional technology.